Gas turbine engines operate by passing a volume of gases through a series of compressors and turbines in order to produce rotational shaft power. High energy gases rotate a high pressure turbine to generate the shaft power. The shaft power drives a high pressure compressor to provide compressed air to a combustion process that generates the high energy gases for turning the high pressure turbine. The high energy gases can also be used to rotate another turbine for additional purposes. In an aircraft engine, a low pressure turbine can be used to generate propulsion, such as directly via thrust, or indirectly via a shaft and fan or propeller. In an industrial gas turbine, a power turbine can be used to drive a shaft for powering a generator that produces electricity.
Each compressor and turbine comprises a plurality of stages of vanes and blades, each vane and blade including an airfoil. In general, stators redirect the trajectory of the air coming off the blades for flow into the next stage. In the compressor, stators convert kinetic energy of moving air into pressure, while, in the turbine, stators accelerate pressurized air to extract kinetic energy. In the compressor, the rotating blades push air past the stationary vanes. In the turbine, the rotating blades extract rotational power from the flowing air.
Typically, blades used in turbines and compressors are removable from the rotor wheel in order to perform maintenance or replace the blades. Thus, various solutions have been implemented to prevent displacement of the blades within the rotor wheel. In one system, a lockwire is disposed near the outer circumference of the rotor wheel to block axial movement of roots of the blades. These designs, however, can experience issues related to circumferential motion of the lockwire. This can, in some instances, compromise retention of the lockwire, potentially allowing axial liberation of the blades. For example, one or more ends of the lockwire can become radially displaced as the lockwire circumferentially rotates, thereby causing ends of the lockwire to be pushed radially inward of the blade roots. Thus, the blades can become unrestrained in the axial direction and can become displaced.
Several attempts have been made to address circumferential displacement of lockwires. U.S. Pat. No. 8,905,717 to Roman-Morales et al. proposes to solve this problem via attachment of tabs onto the lockwire that will restrict lockwire circumferential motion via interference with radial retention features, such as pins, connected to the rotor wheel. U.S. Pub. No. 2014/0112793 to Latimer et al. introduces circumferential stops between ends of the lockwire to prevent circumferential motion the lockwire. U.S. Pat. No. 8,485,784 to Eastman et al. discloses other approaches for restricting circumferential motion via attachment of pins to the lockwire.